KR100978526B1 - Fuel cell system - Google Patents

Abstract

The fuel cell system of the present invention includes a fuel cell body generating power by an electrochemical reaction between a first reactant gas and a second reactant gas, a first gas supply flow path supplying first and second reactant gases to the fuel cell body; A second gas supply flow path and a first gas discharge flow path and a second gas discharge flow path for discharging off-gases of the first and second reaction gases from the fuel cell body, and further comprising a first gas discharge flow path and a second gas discharge flow path. It has a branch flow path branched from one of the flow paths, The off-gas guide | induced from the other gas discharge flow path is distribute | circulated to the said branch flow path, It is characterized by the above-mentioned.

Description

Fuel Cell System {FUEL CELL SYSTEM}

The present invention relates to a fuel cell system.

A fuel cell system is a system that supplies fuel gas and oxidant gas to a fuel cell via a supply path of these gases, and generates electricity by using an electrochemical reaction of these gases in the battery body. Water is generated in the battery main body by this electrochemical reaction, but this water is discharged from the battery main body in a state contained in the oxidant off gas (oxidant gas discharged from the fuel cell main body). Moreover, since fuel gas is normally supplied through the electrolyte of a battery main body, moisture is contained also in fuel off gas (fuel gas discharged from a fuel cell main body).

Therefore, when the temperature of the outside air drops to zero, for example, while the fuel cell system is stopped, moisture in the gas remaining in the valves or pipes installed in the gas flow path of the system condenses. There are cases where the components of the freeze. In such a case, there is a possibility that even after the fuel cell system is started, normal operation cannot be performed even if it can be started or even if it can be started.

As a countermeasure, before stopping the fuel cell system, the oxidant gas path and the fuel gas path of the fuel cell system are purged using the oxidant gas (air) supplied from the compressor to remove residual water. The method is proposed (patent document 1).

[Patent Document 1]

Japanese Patent Application Laid-Open No. 2002-313395

However, even when the system is stopped by using the technique of Patent Literature 1 in the state of discharging residual water in the fuel cell system, if the system is started at a low temperature thereafter, then again by electrochemical reaction in the fuel cell, Water is produced. In this case, since valves and piping arranged in mainstream passages where hot fuel off gas, oxidant off gas, etc. constantly flow, are warmed by direct contact with these gases, there is no possibility of freezing in such a portion during operation. low. However, since the piping and the like provided at a position away from the mainstream passage are not exposed to a high temperature off-gas, they remain at a low temperature close to the outside air temperature even during system operation. Therefore, if the water generated by the electrochemical reaction in the fuel cell comes into contact with a low temperature pipe part or the like after startup, freezing occurs at that site even though the system is in operation. In particular, there is a problem that the system cannot be properly operated when freezing occurs in the piping or the like and the piping is blocked.

SUMMARY OF THE INVENTION The present invention has been made in view of such a problem, and is freezing in a low temperature environment of a component that is located away from a heat transfer component such as a battery body or a flow path of a fuel off gas or an oxidant off gas, and is hard to transmit heat from a fuel cell. It is an object of the present invention to provide a fuel cell system that can effectively prevent the occurrence of a gas.

In order to achieve the above object, in the present invention, the fuel cell body to generate power by the electrochemical reaction of the first reaction gas and the second reaction gas, and the first and second reaction gas to supply the fuel cell body A fuel cell system comprising a gas supply flow path and a second gas supply flow path, and a first gas discharge flow path and a second gas discharge flow path for discharging off-gases of the first and second reaction gases from the fuel cell body, A fuel cell system having a branch flow path branched from one of the first gas discharge flow path and the second gas discharge flow path, wherein the off-gas induced in the other gas discharge flow path can be passed through the branch flow path. do.

In the case of such a system configuration, components such as pipes and valves provided in the branch flow path for one off gas, which are usually freed under a low temperature environment without being brought into contact with the high temperature off gas, have the other gas discharge flow path. Since it warms up efficiently by the heat of the off-gas from, it becomes possible to prevent freezing of these components.

For example, the fuel cell system may include a bypass flow path for guiding off gas of the other gas discharge flow path to the branch flow path. In addition, "guide | induce to a branch flow path" means introducing off gas of a reactive gas directly into a branch flow path, and introducing off gas of a reaction gas in the vicinity of a branch flow path, and transferring the heat which an off gas has to a branch flow path. Includes both meanings of doing By providing such a bypass flow path, the above effects can be obtained more reliably.

Here, the fuel cell system may have an adjusting means for introducing off gas of the other gas discharge flow path into the bypass flow path. In this case, since the off gas can be reliably introduced into the bypass flow path by the adjusting means, freezing of the component parts can be prevented more effectively.

In addition, the solenoid valve is disposed upstream of the branch flow path from the connection point between the branch flow path and the bypass flow path, and the adjustment means is configured to release off gas of the other gas discharge flow path when the solenoid valve is closed. You may operate so that it may introduce into the said bypass flow path. As a result, the off gas of the reaction gas from the bypass flow path can be prevented from flowing back to the branch flow path.

Alternatively, the branch flow passage may have a double pipe structure piping, and one side of the double pipe may allow the off gas of the other reactive gas from the bypass flow passage to flow. In this case, the off gas of the reaction gas does not flow back into the branch flow path, and the above-mentioned solenoid valve is unnecessary.

The branch flow path may be a flow path for discharging a gas containing water treated by the gas-liquid separation means.

Alternatively, the first gas discharge flow path may be connected to the first gas supply flow path, and the branch flow path may be a flow path for discharging the first reaction gas out of the system.

The adjusting means may be a means capable of distributing off gas flowing through the discharge flow path to the bypass flow path and the discharge flow path to which the bypass flow path is connected by adjusting the opening degree. Accordingly, even when the off gas of the reaction gas is introduced to the bypass flow path side, the problem that the power load increases and the fuel economy of the system worsens due to excessive back pressure rise of the off gas discharge flow path can be avoided.

In particular, it is preferable to change the opening degree of the said adjustment means by the temperature and / or outdoor air temperature of the branch flow path to which a bypass flow path was connected. As a result, a more effective freezing prevention operation is possible.

Alternatively, in another aspect of the present invention, the branch flow path has a first solenoid valve, and the branch flow path is connected to the other gas discharge flow path, and the branch flow path is connected to the first solenoid valve and the other gas discharge flow path. Another discharge flow path may be provided in between, and a second solenoid valve may be disposed in the other discharge flow path. In such a system configuration, it is possible to prevent freezing of pipes and valves and the like provided in the branch flow paths without newly installing the bypass flow path and the adjustment means.

In the fuel cell system of the present invention, it is possible to effectively prevent freezing of components such as piping that are located away from the fuel cell and are difficult to transfer heat from the fuel cell, thereby allowing the fuel cell system to operate normally even in a low temperature environment. It becomes possible.

1 is a configuration diagram of a fuel cell system of the present invention;

2 is a flowchart showing the operation of the freezing prevention unit in the fuel cell system of the present invention;

3 is a view showing a second embodiment of the freezing prevention unit in the fuel cell system of the present invention;

4 is a view showing a third embodiment of the freezing prevention unit in the fuel cell system of the present invention.

[Description of Drawings]

1 fuel cell body 2 fuel gas flow path

3: oxidant gas flow path 4: control unit

5: target area 200: high pressure hydrogen tank

201: fuel gas supply passage 203: circulation passage

207: first quarter euro 209: second quarter euro

210: hydrogen pump 220: gas-liquid separator for fuel off-gas

230, 234, 240, 244, 246: solenoid valve

232: pressure reducing valve 242: check valve

250: diluent 301: oxidant gas supply flow path

303: oxidant off-gas discharge passage

305: Compressor 307: downstream branch flow path

309, 344: solenoid valve 325: humidifier

312: gas branch flow path off oxidant

320: gas-liquid separator for oxidant off gas

400: pressure measurement result 401: temperature measurement result

502: bypass flow path 503: discharge pipe

505: adjusting means 510: solenoid valve

EMBODIMENT OF THE INVENTION Hereinafter, embodiment of this invention is described with reference to drawings.

1 shows a configuration example of a fuel cell system according to the present invention. This system has a fuel cell main body 1, and can use the electric power generated in this fuel cell main body 1 as a drive source, such as a vehicle. The fuel cell system also includes a fuel gas flow path 2 for circulating fuel gas in the system, an oxidant gas flow path 3 for circulating oxidant gas (air), and a control unit 4. In the example of FIG. 1, it is necessary to note that the first branch flow path 207 branched from the gas-liquid separator 220 to be described later is used as a part that exhibits the freezing prevention effect of the present invention. Is referred to as the target area 5]. In the following description, a system using hydrogen gas as a fuel gas supplied to a fuel cell will be described as an example.

The fuel gas flow path (hereinafter also referred to as hydrogen gas flow path) 2 is a fuel gas supply flow path for supplying fuel gas from a hydrogen fuel source such as the high-pressure hydrogen tank 200 to the fuel cell body 1, for example. 201 and a fuel off gas discharge flow path 203 for discharging fuel off gas from the fuel cell body 1. However, the fuel off gas discharge flow path 203 is substantially a circulation flow path, and on the fuel cell main body 1 side, the fuel gas supply flow path passes through the gas-liquid separator 220 and the hydrogen pump 210 which will be described later. 201 is connected. The fuel off gas discharge passage 203 is also referred to as a circulation passage 203 thereafter. The first branch flow passage 207 and the second branch flow passage 209 are connected to the circulation flow passage 203.

In the fuel gas supply flow path 201 of the hydrogen gas flow path 2, a normally closed solenoid valve 230 is disposed at the discharge port of the high-pressure hydrogen tank 200, and the fuel cell body 1 flows toward the fuel cell body 1 side. As such, the pressure reducing valve 232 and the normally closed solenoid valve 234 are disposed. On the other hand, in the circulation flow path 203, the normally closed solenoid valve 240, the gas-liquid separator 220, the hydrogen pump 210, and the check valve 242 are arranged in this order as seen from the fuel cell body 1 side. . Moreover, the 1st branch flow path 207 is connected with the gas-liquid separator 220, and the normally closed solenoid valve 244 is arrange | positioned in the middle. The second branch flow path 209 is connected to the circulation flow path 203 between the outlet side of the pump 210 and the connection point A of the circulation flow path 203 and the fuel gas supply flow path 201. The normally closed solenoid valve (purge valve) 246 and the dilutor 250 are arranged in the second branch flow path 209, and the other end of the second branch flow path 209 on the outlet side of the dilutor 250 is disposed. Is connected to the oxidant off-gas discharge flow path 303 described later. The other end of the first branch flow path 207 is also connected to the oxidant off-gas discharge flow path 303.

On the other hand, the oxidant gas flow path 3 includes an oxidant gas supply flow path 301 for supplying an oxidant gas to the fuel cell body, and an oxidant off gas discharge flow path 303 for discharging the oxidant off gas from the fuel cell body 1. ).

The compressor 305 and the humidifier 325 are arrange | positioned in the oxidant gas supply flow path 301. The humidifier 325 is provided in the oxidant off-gas discharge passage 303, and an electromagnetic valve (air pressure control valve) 309 is disposed between the humidifier 325 and the fuel cell main body 1. . In addition, the oxidant off gas discharge flow path 303 has an oxidant off gas branch flow path 312 on the downstream side of the target region 5 described later, and the oxidant off gas branch flow path 312 is the diluent 250 described above. ) Is connected. Further downstream of the oxidant off-gas discharge flow path 303, a gas-liquid separator 320 for oxidant off-gas is provided, and a downstream branch flow path 307 is connected to the gas-liquid separator 320, in which The valve 344 is arranged. However, the diluent 250, the oxidant off gas branch flow path 312 and / or the gas-liquid separator 320, the downstream branch flow path 307, and the solenoid valve 344 may be omitted.

The control part 4 receives the pressure measurement result 400 and the temperature measurement result 401 from the pressure sensor and the temperature sensor provided in the predetermined part of each said flow path, and each valve 234, 240, 244, 246, 230, 232, 309, the hydrogen pump 210, the compressor 305, and the like, are respectively controlled. Moreover, the control part 4 also controls the adjustment means 505 of the target area | region 5 demonstrated later. In addition, in order to make drawing easy to see, a control line etc. are abbreviate | omitted.

Here, the normal flow of the oxidant gas will be briefly described. In the normal operation of the fuel cell system, by operating the compressor 305 by the control unit 4, air in the atmosphere is introduced as the oxidant gas, and the humidifier 325 is opened through the oxidant gas supply passage 301. It is supplied to the fuel cell 1 via. The supplied oxidant gas is consumed by the electrochemical reaction in the fuel cell 1 and then discharged as an oxidant off gas. The discharged oxidant off gas is discharged to the outside via the gas-liquid separator 320 or the like through the oxidant off gas discharge passage 303.

Next, the flow of hydrogen gas will be described. In normal operation, the solenoid valve 230 is opened by the control unit 4, and hydrogen gas is discharged from the high pressure hydrogen tank 200, and the discharged hydrogen gas is passed through the fuel gas supply flow path 201. After the pressure is reduced by the pressure reducing valve 232, it is supplied to the fuel cell body 1 via the solenoid valve 234. The supplied hydrogen gas is consumed in the electrochemical reaction in the fuel cell 1 and then discharged as a hydrogen off gas. After the water is removed from the gas-liquid separator 220 through the circulation flow path 203, the discharged hydrogen off gas returns to the fuel gas supply flow path 201 through the hydrogen pump 210, and then returns to the fuel cell main body ( Supplied to 1). Moreover, since the check valve 242 is provided between the connection point A of the fuel gas supply flow path 201 and the circulation flow path 203, and the pump 210, the circulating hydrogen off gas does not flow back. Normally, the solenoid valves 244 and 246 of the first and second branch flow paths 207 and 209 are closed, but if these valves are opened as necessary, from the respective branch flow paths, the gas-liquid separator 220 The gas containing a lot of treated moisture and the hydrogen off gas which need not be circulated are discharged. These liquids and / or gases are discharged out of the system via the oxidant off gas discharge passage 303.

Next, the configuration and operation of the target area 5, which is also a characteristic part of the present invention, will be described.

The target region 5 has a bypass flow passage 502 branched from the oxidant off-gas discharge flow passage 303 and an adjusting means 505. However, more precisely, the freezing prevention unit 5 indicates a portion surrounded by the broken line in FIG. 1 and includes a part of the oxidant off-gas discharge flow path 303 and a part of the first branch flow path 207. The adjusting means 505 is a device capable of converting the gas flow in two directions.

Usually, in the fuel cell system, in the same portion as the first branch flow path 207 where heat from the fuel cell is hard to transfer, moisture remaining in the flow path may freeze, and the flow path may be clogged to prevent proper operation. This phenomenon is particularly remarkable when the fuel cell system is used in a low temperature environment such as, for example, 0 ° C, and the pipe may freeze in the above portion even when the system is in operation. However, in the target region 5 of the present invention, the control unit 4 controls the adjusting means 505 provided at the contact point between the oxidant off-gas discharge flow path 303 and the bypass flow path 502. Therefore, it can distribute to the bypass flow path 502. FIG. Therefore, it is possible to prevent freezing of the first branch flow path 207 by circulating the heat of the high temperature oxidant off gas through the bypass flow path 502. In particular, in the case where the adjusting means 505 is a variable guide device, the amount of oxidant-off gas flowing through the bypass flow path 502 can be adjusted. In addition, the oxidant off gas passed through the bypass flow path 502 then joins the oxidant off gas discharge flow path 303 again through the first branch flow path 207 and is discharged out of the system.

This operation will be described in detail with reference to the flowchart shown in FIG. 2.

First, in step S10, the outside air temperature or the target piping temperature (in the system configuration of FIG. 1, the piping temperature of the first branch flow path 207) is measured, and the control unit 4 measures the measurement temperature 401 in advance. By comparison with the set threshold value, it is determined whether the freezing prevention operation is necessary. When the measured temperature exceeds the threshold, the operation of the adjusting means 505 by the control unit 4 is not performed, and the oxidant off gas is not flowed through the bypass flow path 502, and the oxidant off gas is discharged as usual. Only the flow path 303 flows and is discharged. On the other hand, when the measurement temperature 401 is below the threshold value, it is determined by the controller 4 that the freezing prevention operation of the target portion is necessary, and the flow advances to the next step S20.

In step S20, the open / closed state of the solenoid valve 244 of the gas-liquid separator 220 is confirmed. When the solenoid valve 244 is closed, in the next step S30, the adjusting means 505 is operated to branch off the oxidant off gas (usually a part thereof) to the bypass flow path 502 side, and this hot gas is By flowing, the piping of the 1st branch flow path 207 becomes warm, and freezing is prevented. Here, the opening degree of the adjusting means 505 (ratio of flowing off gas to the bypass flow path 502 side: 100% means that all oxidant off gas flows to the bypass flow path 502 side) is the outside air temperature. Or you may change according to the measured value 401 of target piping temperature. In principle, as the opening degree of the control means 505 increases, the back pressure rises, leading to deterioration of fuel economy due to an increase in the load of the power (compressor 305 or the like). On the other hand, when the opening degree of the adjustment means 505 is low, the time until the freezing prevention effect is acquired becomes long. Therefore, when the opening degree of the adjustment means 505 after an operation is constant, any one effect will appear remarkably. Even in such a case, when the control part 4 is set as the structure which changes the opening degree of the adjustment means 505 suitably, it becomes possible to simultaneously prevent the freezing of a low temperature part, and to suppress fuel deterioration. This operation can be performed by storing in advance the relationship between the outside temperature or the target pipe temperature and the opening degree of the adjustment means 505 in the control unit 4. As a result, for example, when the target pipe temperature is significantly lowered by the controller 4, the opening degree of the adjusting means 505 is increased, and the target pipe temperature is increased by heat exchange in the oxidant off gas bypassed. After starting, it becomes possible to perform the operation of gradually decreasing the opening degree of the adjusting means 505 in accordance with the temperature. On the other hand, when it is determined in step S20 that the solenoid valve 244 is open, the adjusting means 505 is not operated. This is because when the oxidant off gas flows into the bypass flow path 502 from the oxidant off gas exhaust passage 303 with the solenoid valve 244 open, this gas passes through the solenoid valve 244 to the first branch. This is because the flow path 207 may be flowed back.

The above steps are basically carried out repeatedly during operation after the start of the fuel cell system, so that it is possible to avoid freezing of the low temperature portion at all times.

Another embodiment of the target region 5 by the fuel cell system of the present invention is shown in FIGS. 3 and 4.

In the 2nd Example of the target area | region 5, as shown in FIG. 3, the piping which comprises the 1st branch flow path 207 has a double pipe structure. That is, in this embodiment, the branched oxidant off gas flow path in the above-described embodiment is composed of a bypass flow path 502a and a flow path 502b on the outer circumferential side of the double pipe. In addition, the inner tube of the double tube serves as a flow path of water or the like processed by the gas-liquid separator 220 and serves as the first branch flow path 207 described above. In this case, since the oxidant off gas branched from the oxidant off gas flow path 303 to the bypass flow path 502a flows outward of the double pipe, the inner pipe of the double pipe is formed by heat exchange with the oxidant off gas. Freezing is prevented. In this structure, when the control means 4 operates the adjusting means 505, there is an advantage that it is not necessary to consider the open / closed state of the solenoid valve 244 disposed downstream of the gas-liquid separator 220. This is because the gas does not flow back to the gas-liquid separator 220 even when the oxidant off gas is supplied to the bypass flow passage 502a in the state where the solenoid valve 244 is open. Therefore, more efficient freeze prevention operation can be performed.

In the third embodiment of the target area 5, it is not necessary to newly install the bypass flow path 502 (or 502a) as in the above two embodiments. In this case, as shown in FIG. 4, the target region 5 includes a pipe 207c constituting the first branch flow passage 207, a discharge pipe 503 for discharging the branched oxidant off-gas, and a discharge pipe ( And a solenoid valve 510 connected to 503. In a normal state, the solenoid valve 510 and the solenoid valve 244 are closed. In addition, in the case of discharging the water or the like processed by the gas-liquid separator 220, only the solenoid valve 244 is opened, and the pipe 207c is used as the branch flow path 207 for discharging the water treated by the gas-liquid separator 220. do. The flow of the fluid at this time is shown by arrow P. FIG. On the other hand, in the freezing prevention operation, the pipe 207c is used as a bypass flow path of the oxidant off-gas discharge flow path 303. That is, at the time of freezing prevention operation, the solenoid valve 244 is closed, the solenoid valve 510 is opened, and the oxidant off gas branched and supplied from the oxidant off gas discharge flow path 303 is indicated by arrow Q in the pipe 207c. Flows in the direction of, and is discharged from the discharge pipe 503 after heat exchange is performed in the pipe 207c. In this structure, when the solenoid valve 510 is closed, the oxidant off gas does not distribute the piping 503. On the other hand, when the solenoid valve 510 is open, since the back pressure of the piping 503 becomes lower than the oxidant off-gas discharge flow path 303, the oxidant off-gas will also flow to the piping 503 side. Thus, the adjustment means 505 described above becomes unnecessary. In addition, since there is no need to provide a new dedicated bypass flow path in the existing fuel cell system, the system can save space.

In each of the embodiments of the present invention, the first branch flow path 207 is selected as the portion (target region 5) for freezing prevention of the fuel cell system. However, it will be apparent that the present invention can also be applied to other freezing parts, such as the second branch flow path 209, for example.

In addition, in the above description, the structure which prevents freezing of the branch flow path connected to the flow path of fuel off gas using the oxidant off gas was demonstrated. However, in this invention, it is also possible to prevent freezing of the branch flow path (for example, the downstream branch flow path 307) connected to the flow path of the oxidant gas by using a fuel off gas on the contrary. In this case, if necessary, the term "oxidant off gas" or "oxidant gas" in the description of the above embodiments or the prefix is referred to as "fuel off gas", "fuel gas" or "hydrogen off gas", and "hydrogen gas". By rewriting with or vice versa, other configurations of the present invention may be further understood.

In addition, the structure of the fuel cell system used for description of this invention is an example, Comprising: It does not limit this invention. For example, in an actual fuel cell system, other components such as solenoid valves and piping may be installed in parts not shown, and on the contrary, some components shown in FIG. 1 may be omitted. It should be noted that

In addition, this application claims the priority based on Japanese Patent Application No. 2005-349337 for which it applied on December 2, 2005, and uses the whole content of the same Japanese application by reference here.

Claims (10)

A fuel cell body generating power by an electrochemical reaction between a first reaction gas and a second reaction gas, a first gas supply passage and a second gas supply passage for supplying the first and second reaction gases to the fuel cell body, and a fuel A fuel cell system comprising a first gas discharge flow path and a second gas discharge flow path for discharging off-gases of first and second reaction gases from a battery main body, Moreover, it has a branch flow path branched from one of a 1st gas discharge flow path and a 2nd gas discharge flow path, The off-gas guide | induced from the other gas discharge flow path can be distribute | circulated in the said branch flow path, The said branch flow path, A fuel cell system, characterized in that the flow path for discharging the gas containing water treated by the gas-liquid separation means. The method of claim 1, And a bypass passage for guiding off gas of the other gas discharge passage to a branch passage. 3. The method of claim 2, And an adjusting means for introducing off gas of said other gas discharge flow path into a bypass flow path. The method of claim 3, wherein The solenoid valve is arranged upstream of the branch flow path from the connection point between the branch flow path and the bypass flow path, and the adjustment means is configured to receive off gas of the other gas discharge flow path when the solenoid valve is closed. And a fuel cell system operable to be introduced into the bypass flow path. 3. The method of claim 2, The said branch flow path has the piping of a double pipe structure, The fuel cell system characterized by the off-gas of the other reactive gas from a bypass flow path being distributed in one of the double pipes. delete The method of claim 1, The first gas discharge passage is connected to the first gas supply passage, and the branch passage is a passage for discharging the first reactive gas out of the system. The method of claim 3, wherein The adjustment means is a fuel cell characterized by distributing an off gas flowing through the discharge flow path to a discharge flow path to which the bypass flow path and the bypass flow path are connected by adjusting the opening degree. system. The method of claim 8, The opening degree of the adjustment means is changed by at least one of the temperature of the branch flow path to which the bypass flow path is connected and the outside air temperature. The method of claim 1, The branch flow passage has a first solenoid valve, The branch flow path is connected to the other gas discharge flow path, A fuel cell system according to claim 1, wherein another discharge passage is provided between the first solenoid valve and the other gas discharge passage, and a second solenoid valve is disposed in the other discharge passage.

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